1. Field of the Invention
The present invention relates to a medical imaging apparatus in which a gamma camera apparatus and an ultrasonic apparatus are integrated into one unit.
2. Description of the Related Art
An ultrasonic apparatus is used in the medical field, for example, in which an ultrasonic wave is emitted onto an examinee and a tomographic image of the examinee is obtained on the basis of a reflected wave therefrom. The ultrasonic apparatus generates the tomographic image based on a time difference required for the arrival of the reflected wave caused by a difference in acoustic impedance among respective tissues of the examinee. The ultrasonic apparatus is widely utilized since it is compact and excellent in portability and can recognize the cross-sectional shape of the tissue while keeping out of contact with the examinee.
However, it is impossible to recognize a living tissue having a high acoustic impedance, for example, the internal structure of a bone tissue. Further, the acoustic impedance is low in the blood and the lymph as compared with other living tissues. Therefore, it is also difficult to recognize a state of the blood and the lymph.
In the meantime, there have recently been developed gamma camera apparatus (Anger camera apparatus) for detecting gamma rays emitted from a radioisotope (RI) administered to an examinee with a plurality of detectors arranged in a plane and a scintillator, and constructing two-dimensional internal information of the examinee based on the detected gamma rays. When the gamma camera apparatus is used, it is possible to obtain a vivid image of a specified tissue which has absorbed the radioisotope.
One gamma camera apparatus that has been proposed has a coded aperture plate having a number of apertures defined therein according to given rules and disposed in front of a scintillator, and constructs three-dimensional internal information of an examinee based on the information obtained from the coded aperture plate. For details, reference should be made to “Coded Aperture Emission CT Using M-array”, Transactions of the Society of Instrument and Control Engineers, Vol. 28, No. 4,426/432 (1992), and “Three dimensional reconstruction of 99mTc distribution by using coded aperture CT”, Instrument department of the Society of Instrument and Control Engineers, 17th sensing forum (2000).
When the gamma camera apparatus described above is used, it is possible to obtain information of the tissue where the radioisotope is distributed. However, a considerably skillful technique is required in order to recognize the arrangement relationship between the tissue and other tissues of the examinee.